Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Further, as an air-conditioning apparatus which is applicable to such a vehicle, there has been developed an air-conditioning apparatus which includes a compressor to compress and discharge a refrigerant, a radiator disposed on a vehicle interior side to let the refrigerant radiate heat, a heat absorber disposed on the vehicle interior side to let the refrigerant absorb heat, and an outdoor heat exchanger disposed outside a vehicle interior to let the refrigerant radiate or absorb heat, and which is capable of changing a heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated in this radiator absorb heat in the outdoor heat exchanger, a dehumidifying and heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated in the radiator absorb heat only in the heat absorber or in the heat absorber and the outdoor heat exchanger, a cooling mode to let the refrigerant discharged from the compressor radiate heat in the outdoor heat exchanger and let the refrigerant absorb heat in the heat absorber, and a dehumidifying and cooling mode to let the refrigerant discharged from the compressor radiate heat in the radiator and the outdoor heat exchanger and let the refrigerant absorb heat in the heat absorber (e.g., see Patent Document 1).
Here, a conventional air-conditioning apparatus for vehicle selects and changes respective operation modes of the above heating mode, dehumidifying and heating mode, cooling mode and dehumidifying and cooling mode in accordance with a combination of an outdoor air temperature Tam at this time and a target outlet temperature TAO (a target value of a temperature of the air to be blown out to the vehicle interior).
On the other hand, depending on an environment of a vehicle or a condition such as a predetermined temperature, an optimum operation mode is present in the air-conditioning apparatus, but there has been the problem that the optimum operation mode is not necessarily selected in such conventional change control. To eliminate such a problem, in Patent Document 1, the operation mode is changed depending on whether heat radiation in the radiator or heat absorption in the heat absorber becomes excessive or runs short, or the like.